The present disclosure relates to a digital microscope apparatus that captures an enlarged image of a sample such as a living body sample as an enlarged image, and to a method of searching for an in-focus position thereof and a program.
In the past, in order to observe the whole of a sample with use of a digital microscope apparatus, images of small areas that partition an area containing a sample on a glass slide are captured by a enlarging imaging system and such images of the respective small areas are connected to one another to generate one large image.
For a focusing system in which an objective lens of the enlarging imaging system is focused on a pathological sample serving as an imaging target, autofocusing (AF) is adopted. For example, the following autofocusing is disclosed: a focal position of the objective lens in the enlarging imaging system is moved in an optical axis direction at predetermined intervals, images are captured at the respective moved positions, and a position at which an image having the highest contrast in the captured images is captured is detected as an in-focus position (see, for example, Japanese Patent Application Laid-open No. 2011-197283). This type of focusing system is called “contrast AF.”
Although the contrast AF provides relatively high accuracy in focal point, the contrast AF performs repetitive movements and evaluations of the focal position of the objective lens in order to search for the optimal focal position. Consequently, it takes a relatively long time to obtain the optimal focal position.
In this regard, a microscope apparatus that adopts a “phase difference AF” in which light taken through an objective lens is split into two light beams by a splitter lens and the position and direction of a focal point is determined based on the interval between two formed images is also disclosed (see, for example, Japanese Patent Application Laid-open No. 2011-090222). The phase difference AF can provide a focal position at higher speed than the contrast AF without the search for a focal position. Conversely, there is a possibility that the accuracy is lowered due to the size of an object within the imaging surface or due to the number of tissues.